86_RedRider

Quick question, are the secondary valves on a '70 350/300 stock carb, mechanical or vacuum operated?

Thanks,
Joe

Eddie 70

Pretty sure those are vacuum.

page62

If we're talking about the Quadrajet here, the secondary throttle plates are mechanical. BUT, the air valves on top open up according to the amount of air flowing through them -- that's what makes the QJet unique.

gerry72

Actually, Holley and Barry Grant are the only manufacturers to use a vacuum secondary. All the others use an air valve, like Page says, to allow the secondary to respond. The Quadrajet is one of the best designs since it allows easy tuning on the opening. And on the Q-jet, the air valve's position also affects the secondary metering rods so the more the door is open, the more fuel is metered into the jeg. The Carter AFB and Edelbrock variants use a counter-balanced weighted door that requires mass to physically be removed (like drilling or grinding and it's awfully hard to go back once you take it off) off the counterbalance to tune the door opening. The Carter AVS and Edelbrock equivalent have an air door similar in tuning to the Quadrajet.

Don't know why everyone bangs on the Q-jet. It's nearly infinitely tuneable.

86_RedRider

thanks. my father-in-law was asking if i could find out. he wasn't sure if they were working or not, i told him to let me drive it to find out. :D i don't think he's taken it over 60 and he hasn't accelerated fast enough either. He's only had it a little over a month now. i have actually driven it, and more and more, it makes me want to get a C3 as a stable mate for my 86.

lars

Correct as stated by the San Antonio guys :yesnod: